A water softening device softens hard water, as disclosed in Patent Document 1, by passing the hard water through a cation exchange resin to adsorb hardness components, such as a calcium ion, a magnesium ion or the like, to the cation exchange resin, and then regenerates the cation exchange resin by inserting chemicals, such as sodium chloride and the like, into the cation exchange resin.
Because chemicals should be regularly purchased and inserted into the water softening device to regenerate the cation exchange resin of the water softening device, there is a problem in which costs and time are required.
The water softening device disclosed in Patent Document 2 includes a resin chamber having a cation exchange resin and an anion exchange resin and a pair of electrodes arranged by placing the resin chamber therebetween. The water softening device may regenerate the cation exchange resin without using chemicals and the like by applying a voltage to the resin chamber using the electrodes.
A principle in which the cation exchange resin is regenerated in the water softening device will be described.
Because the resin chamber of the water softening device has the cation exchange resin and the anion exchange resin, when the voltage is applied to the resin chamber by the pair of electrodes, water is decomposed between the cation exchange resin and the anion exchange resin, and thus a hydrogen ion and a hydroxide ion are generated.
In this case, the hydrogen ion is exchanged with hardness components, such as a calcium ion or a magnesium ion, adsorbed to the cation exchange resin to regenerate the cation exchange resin.
However, a strongly acidic cation exchange resin or a strongly alkaline anion exchange resin is used in the ion exchange resin used in the water softening device to efficiently adsorb hardness components contained in water, but there is a problem in that it is difficult to regenerate the ion exchange resin after the water is softened.
Because hardness components are easily adsorbed to the strongly acidic cation exchange resin, it is difficult to exchange between the hydrogen ions generated by water decomposition and the hardness components once the hardness components in water are adsorbed.
Also, although anions, such as a chloride ion, in water are easily adsorbed to the strongly alkaline anion exchange resin, it is difficult to exchange between the hydrogen ions generated by water decomposition and the anions once the anions are adsorbed.